The gonad of the nematode worm C. elegans originates as a four-cell primordium, morphologically identical for both sexes, but soon after the completion of embryogenesis develops into two very dimorphic organ structures. Although the largely invariant cell lineages have been well characterized for gonadal development in both sexes, the genetic pathways involved in the sex-specific development remain largely unknown and few sex-specific gonadal regulators have been identified. All somatic sexual dimorphism in C. elegans, including that of the gonad, is under the control of the TRA-1 transcription factor. (XX tra-1 null animals are fertile pseudomales.) In the nematode, TRA-1 gonadal targets remain unknown, and only a handful of TRA-1 targets have been identified in non-gonadal tissues, most of which are conserved developmental regulators whose human counterparts have important roles in development and cancer. For example, the C. elegans TRA-1 target MAB-3 belongs to the DM domain family of proteins. DMRT1, a DM domain family member, is required for normal testis development in the mouse and has been implicated jn testicular cancer. The objective of this proposed research is to uncover the genetic pathways and molecular mechanisms involved in the sexually dimorphic development of the C. elegans gonad, focusing on direct targets of TRA-1. In Aim I, microarray-based strategies will be used to identify the sex-specific gonadal transcriptome. Transcription profiles of the developing somatic gonad will be obtained at two different developmental time points for both sexes of nematodes, allowing for the identification of sex-specific transcriptional enrichment. The objective of Aim II is to analyze the roles of the sex-specific regulators during gonadal development. To identify which sex-specific transcripts are directly regulated by TRA-1, and presumably at the top of the hierarchy of gonadal regulators, the transcriptome data set will be compared with a TRA-1 ChlP-on-chip data set that is currently being generated. Expression profiling, mutational analysis, and RNAi depletion studies will be employed to validate whether the identified genes are directly regulated by TRA-1 within the gonad, and to further determine their molecular roles and genetic interactions. PUBLIC HEALTH RELEVANCE: Genetic or environmental factors can lead to disruption of genes involved in development resulting in serious dismorphogenesis and cancer. In humans the reproductive system is a common site of these problems: infertility affects ~10% of the population and testicular cancer is the most common cancer in young men. This proposed research explores the sex-specific development of the nematode worm C. elegans gonad as a paradigm for human gonadal development and reproductive health.